Questions And Answers

Can dry (<20%rh) neon gas slowly passing over polyurethane coated electronics modules generate a static charge in the polyurethane? The module construction is polyimide MLBs laminated to an aluminum frame. The frames are tied to chassis ground and the neon is always in contact with chassis ground. - Anonymous, Cambridge, MA

Answer

No. Gases do not charge. They do not have enough mass to initiate triboelectric generation on the polyurethane (or any surface). It is the large-mass impurities that the gas (neon) may carry that can tribocharge the contacting surface(s). "GASES DO NOT CHARGE! It is well known that early on, the aerospace industry learned that the surface of an aircraft would charge up considerably when flying within our troposphere. Re-fueling required an operator to attach a grounded cable first to the aircraft before bringing a fuel hose near the craft. In later designs, the wings deployed corona discharge points on the trailing edges of the wings to help neutralize the charging. What was happening to cause the aircraft to charge? Simply put, the surface of aircraft had undergone triboelectric charging due to the collision with impurities and other large (non-gases) particles that are also present in the air. These large, actually huge particles compared to oxygen, nitrogen and argon atoms, collide with the fuselage and wing surfaces and can both depart and extract a surface charge. Niels Jonassen (Mr. Static) had early on (1954) been part of an extremely sensitive experiment to help investigate a fatal explosion involving an anaesthetic machine at a local hospital. This experiment utilized a Wolf electrometer, and demonstrated that the flow of oxygen, cyclopropane and mixtures thereof did not show any signs of charging. The cause of the explosion was later found to be due to the tribocharging and consequent ESD of the metal pin and rubber bag that comprised part of the anaesthetic machine."